Ejection of hypervelocity binary stars by a black hole of intermediate mass orbiting Sgr A*

TL;DR

This paper investigates the potential ejection of hypervelocity binary stars by an intermediate-mass black hole orbiting Sgr A*, providing estimates on their expected numbers and implications for detecting such events.

Contribution

It introduces a hybrid computational approach to estimate the ejection rate and total number of hypervelocity binaries produced by an IMBH near Sgr A*.

Findings

Expected HVB ejections range from zero to a few dozen.

Non-detection of HVBs does not exclude recent IMBH-Sgr A* in-spiral events.

The study constrains the likelihood of observing HVBs from an IMBH in the Galactic Center.

Abstract

The discovery of hypervelocity binary stars (HVBs) in the Galactic halo would provide definite evidence of the existence of a massive black hole companion to Sgr A*. Here we use an hybrid approach to compute the rate of ejection and the total number of HVBs produced by a hypothetical intermediate-mass black hole (IMBH, M_2<10^5\msun) orbiting Sgr A*. Depending on the mass of M_2 and on the properties of binary stars in the central parsec of the Milky Way, we show that the number of undisrupted HVBs expected to be expelled from the Galactic Center before binary black hole coalescence ranges from zero to a few dozens at most. Therefore, the non-detection of stellar binaries in a complete survey of hypervelocity stars would not rule out the occurrence of an IMBH-Sgr A* in-spiralling event within the last few 10^8 years.